The present invention relates to a toggled switch and a sheet transport apparatus containing such a switch. In particular, it is directed to a switch that provides a positive switch actuator system in one mode of operation and a passive actuator during another mode of operation. In a particular application, the switch is used in one or more of the paper paths in an automatic electrostatographic printing machine.
In an electrostatographic reproducing apparatus commonly in use today, a photoconductive insulating member is typically charged to a uniform potential and thereafter exposed to allight image of an original document to be reproduced. The exposure discharges the photoconductive insulating surface in exposed or background areas and creates an electrostatic latent image on the member which corresponds to the image areas contained within the usual document. Subsequently, the electrostatic latent image on the photoconductive insulating surface is made visible by developing the image with developing powder referred to in the art as toner. Most development systems employ a developer material which comprises both charged carrier particles and charged toner particles which triboelectrically adhere to the carrier particles. During development the toner particles are attracted from the carrier particles by the charge pattern of the image areas in the photoconductive insulating area to form a powder image on the photoconductive area. This image may subsequently be transferred to a support surface such as copy paper to which it may be permanently affixed by heating or by the application of pressure. Following transfer of the toner image to a support surface, the photoconductive insulating member is cleaned of any residual toner that may remain thereon in preparation for the next imaging cycle.
Commercial applications of this apparatus have become increasingly complex. As a result, it has become increasingly important to determine the location of paper or copy sheets in such automatic apparatus at any particular point during the imaging cycle or position of the sheet in the imaging path. This function has typically been performed by a variety of switches, detectors, sensors which detect the presence or absence of a copy sheet in one position to send a signal to the machine timing logic informing it that the sheet is or is not at a particular point in its transport path corresponding to the correct position in the timing cycle so that it can react appropriately by maintaining the automatic reproducing machine in operation or terminating the printing run or even shutting the machine down. These sensors or switches can be used to determine whether the copy sheet has left a particular station on time has arrived on time, or at any particular time is present and thereby accurately inform the machine logic. As a result of the detection of the presence and/or absence of the copy sheet at a particular location at a particular point in the timing cycle, any one of a variety of jam situations may be detected by the machine logic and their location flashed on a display to enable the operator to know the location to facilitate removal of the jammed copy sheet.
Such switches or sensors frequently have a member or arm which extends into the paper path to be contacted or displaced by a sheet being fed along the path. When a paper jam does occur, it must be removed before normal resumption of printing activity with the automatic machine may continue. During removal of a jammed sheet, it is important to prevent damage to the jammed sheet and in particular to avoid tearing the sheet into more than one piece, one of which may not be readily easily removable by a casual operator. It is particularly important that the copy sheets not be pierced and torn in portions of the paper path where access is either very difficult, time consuming or may require the attention of a skilled operator or repairman. Unfortunately, many of the above referenced switches with arms or other members extending into the paper path suffer from difficulties with regard to piercing and tearing copy sheets and creating the jam removal problems referenced above. It is to these problems to which the present invention is directed.